Carl Fausett

Spent 4 hours at the Dyno today with my track car (affectionately known as the Great White Shark, sometimes referred to as "Bizzaro 928" because everything on this car seems to work backwards) – made many adjustments, changed pulleys, tweaked settings and picked up almost 50 HP more than I had 1 week ago at the Autobahn event.

DISCLAIMER: please remember that these results are not from any of the regular kits we sell. This 928 and I are “off the page” and experimenting with strange things that no one in their right mind would repeat.

Two dyno charts attached – the ones labeled “Carl2.73 pulley” were made using a 2.73” pulley on the XB-1a Gear-driven 1200 CFM blower I am using on this car. The dyno pulls from the 2.93” pulley (larger pulley produces less boost) are on the other chart.

General Setup: DynoJet brand dyno with only SAE correction on. Smoothing set to 2; with smoothing off the numbers were all higher by 1 HP or so, but this is easier to read. “Smoothing” averages the peaks and valleys and the posted figure is a little lower as a result. Boost was measured at two locations – right at the outlet of the intercooler just before the motor, and in the central intake plenum (after the throttle body).


Comments about Carl2.93pulley.bmp:
AT TIRE: 380hp, 392 ft lbs torque
AT ENGINE: 437 HP, 451 ft lbs torque

This pulley on this blower produced 8 psi at the intercooler exit, and 6 psi in the center plenum.

We discovered that we could fuel to a 12.5:1 A/F ratio all the way to 6200 RPM.

The HP peak was back at 5500 RPM, and the peak torque was at about 4750 RPM.

You will notice the A/F ratio is very rich at speeds under 4300 RPM – but that gave us the nice flat A/F ratios from 4500 to 6000 RPM. When we tuned it for the bottom end, we lost fuel at the top.

This suggests its time to change the taper in the CIS air-flow venturi, or change air-flow shoe altogether to one with a steeper wall. Frankly, even as rich as it was under 4300RPM, it ran just fine down there and would still be street-able.

Carl Fausett

Comments about Carl2.73pulley.bmp:

AT TIRE: 406hp, 419 ft lbs torque

AT ENGINE: 467 HP, 482 ft lbs torque

As expected, the smaller SC pulley produced more boost – but the CIS system ran out of fuel at the top end.

This pulley on this blower produced 10 psi at the intercooler exit, and 8 psi in the center plenum, consistent with the 2 psi drop in pressure going thru the intake shoe as with the other pulley.

We tried every trick in the book to get more fuel thru the injectors at the top end and just could not get ‘er done – and came away with the feeling that we may have found the ceiling for how much a CIS mechanical injector can spray.

We were able to confirm that fuel delivery was not a problem – we had the fuel at the motor – we just could not get the mechanical injectors to take anymore.

The mechanical injectors for this system come in only one model and size – there is no “bigger injector” to move to. There is a CIS injector that Mercedes Benz used for their 420 HP CIS installs, but it is shorter and when installed in our manifolds it is severely shrouded (BTDT).

Frankly, I can take one step back to the larger pulley that produces a little less boost, fuel to 6200 RPM, and go racing at 437 HP 451 ft Lbs Torque and be competitive.

The lines get all squiggly above 5000 rpm because we jumped off the throttle when we started to go that lean, and the dyno recording had not yet been stopped. The drum does not like to be decelerated by the car... records like that when you do.

Hope you find all this interesting….

FlyingDog

You state that you hit the max flow of the injectors. That would be the max flow pushing against ~8psi of boost. If you created a more efficient intercooler (not saying yours isn't efficient), you could lower the boost with the same air mass and get more fuel flow for more HP. Do you think that would be possible to do on your car? How are the air temps before and after the IC?

1slo928

which cis are you using? I have the smaller 79 on my euro is yours the larger one?

Dennis Wilson

Carl,

Instead of changing the taper on the air horn, wouldn't it be better to install two additional cold start valves that start kicking in at 4K rpm?

Dennis

Carl Fausett

1slo928 -

I am using the larger Euro runners, plenum, throttle body, valves and camshafts.
The fuel distirbutor on the euro was larger, but not large enough, so I had this fuel distributer re-machined to flow 30% more fuel than OEM. We also saw (2 years ago) the the solid fuel lines to each injector on the Euro were largher in ID than the US version - but again; not large enough and the ones on this car are all -4AN

FlyingDog-

When the injectors are at 100 psi or more fuel pressure on one side, beleive me the 8 psi of air pressure on the other side of the injector is not stopping the fuel flow. They do have a limit as to how much fuel can pass through their orifice - and we went from 100 psi to 120 psi to 140 psi without gain. They simple had achieved max flow... (at least thats what I think today.... tomorrow I mioght find a new, better answer. For now, this is the only explanation that seems to fit and explain what we saw) ;-)

Lance J

LP injection or go to Water injection!!!!!!!!!!!!

FBIII

The limitation on L jet under NA conditions has been the floppy door, small runners and small throttle valve. Under a blown situation would that system provide a better platform for larger gains? You could always upgrade to the Euro S plenum and larger throttle valve. I don't think the limitation in this instance would be fuel flow.

FlyingDog

Assuming linear fuel flow that would be 8% less at 100psi. Since fuel flow is not linear with increases in prssure, the 8% pressure difference would have a greater impact on flow when subtracted from 100psi than added to it. Also, the high pressures could be causing restriction of flow, but that kind of stuff is way beyond me.

What else uses similar mechanical injectors? Diesel injector open pressure would be too high. Aircraft engines?

Carl Fausett

Dennis - yes, that is a possibility. In this dyno chart we do have a 9th injector firing beginning at about 4500 RPM. It gets its fuel from the control-side of the WUR - so it actually lowers the control side pressure when it fires, thereby richening the mixture to all 8 regular injectors too. That's the trick to ensure even fuel distribution.

You can see we have it timed to add-in very well - you do not see a sudden jump or dive in the AF ratios. We have it tuned to a T and it blends in perfectly.

At the Autobahn, I reached over and turned on the 9th injector while Mark Anderson was driving my car (faster and harder than I was, I might add!). Wanted to see if he'd notice or report any break in the throttle, cough, hesitation, whatever. There was none.

Today - we turned off the 9th injector and did a pull just to get a baseline from it - and crossed from "rich" into "lean" almost 800 RPM sooner. It really works.
But - the cold start injector will not cut it - I had one flow tested and I forget the number but its something like 16 lb/hr. I had a 35 lb/hr injector made for me and thats what we are using at the moment. I have been reluctant to drill and install another injector mount at the rear of the plenum - looking for other solutions - but that may be what it comes down to.

FBIII - if I was to scrap all this CIS stuff and go with EFI, I would not move to L-Jet - I'd jump over L-Jet and go to LH-Jet. The highest HP and Torque numbers have been 32v LH Jet, and when Kevin (my customer) posts his 16v LH-Jet numbers in the next week I think it will be very impressive also. I think LH-Jet is the finest, most tune-able system installed in these cars.

But, after 4 years of supercharging these cars... L-Jet and K-Jet, Intercooled and non-intercooled... and assisted customers with same - I have never seen L-Jet produce these numbers I just put up today... In my opinion, I think L-Jet has more and harder limitations that would have to be overcome.

FlyingDog - you are right on it - higher pressure after we have hit fluid backpressure at the orifice will cause even lower flow. I like the way your thinking... my search for higher-flowing CIS injectors continues.... as I said I bought and played with the only other one I could find - and it wass too short to peak into the air stream correctly. I toyed with milling and changing my intake runners to match - but decided against it.

Another option would be to find a guru who can dis-assemble these injectors and modify them... but I have not found that guy either.

Anybody know what the 1997 Porsche 930 Turbo (CIS, about 430 HP) used? I just remembered that one tonight, going to look into it tomorrow.

Thanks guys for all the input --- I wanted to be in the "500+" (HP) club, and I thought today might be the day.... just missed it by 33 HP.

Dennis Wilson

Carl,

Don't know what the 930 CIS used but the 924 GTR used two mechanical injectors per cylinder to produce 375 hp at the wheels. They actually used a 928 fuel distributor. Didn't realize the cold start injectors were only one bar but it does make sense.

Other possibilities include using two extra mechanical CIS injectors wired with a gate (frequency) type valve. These could be connected to the primary fuel line or to the WUR to further reduce control pressure. If you are using a WUR off a US CIS, switch to a euro version that further reduces control pressure when a drop in intake vacuum is sensed. The vacuum line for this will need to be sourced in the intake stream before the charge.

Have you actually measured the pressure at the injectors? A stock fuel pump will only flow 6 bar (90 lbs). Upgrading to a 6.5 bar Pierburg and removing a shim from the pressure regulator would probably help the upper end but may affect driveability.

One last option is to convert to a late model (up to 95) MB V-8 CIS fuel distributor? These are expensive but they allow pressure adjustment for each injector.

Dennis

SMTCapeCod

Interesting. This is how my N/A car runs....sooty rear bumper and hard starts yields best performance in the 'rah' range. Makes me crazy, as you said, its driveable but when its lean enough to be clean it leaves a lot of HP on the table.

Maybe using an add-on single electronic injector for the enrichment would provide more and more variable augmentation than sticking with a mechanical injector?

The adjustable fuel distributors may not be so hard to come by- I know that I got one from a dismantler and my assumption was that some of the Bosch rebuilds came that way. It doesn't sound like it would be likely to flow more than your already-modified distributor. Hm....and lambo 12 cylinder FDs? I gues those would have less flow per cylinder too given displacement.

Its an interesting tutorial about the extent to which many US and Euro parts are not really interchangeable. Hope the vendors take note. Guess I should check the number on my FD, or get one of my defunct spares rebuilt to euro specs-- if thats even possible. A modified tunable unit would just get me into deeper trouble...I need less variables, not more..

Carl Fausett

Dennis - thanks for your suggestions. My bad - I should have explained all that has been done to yield the performance numbers I have. You have suggested many things that have already been done or tried long ago - so at least you are right on target.

Bit pressed for time at this moment - but I will try to publish a bit of a list soon.

Lance J

A CIS fuel pump us will flow 8 bar
theres a ballistic resistor on the fuel pump that upon start-up it ups the fuel pressure higher than normal. we can create a knock activated box that will put the fuel pump in start-mode and up the pressure. But like Carl Fausett said his hit the limit. So that brings in the upgrade of the NOS setup Mark Kilbort talk's about have a nozzle for each run. but instead of NOS it can be Water injection. This makes it like your running race gas. But the air is dense due to the evaporation of the water. giving you more HP per Psi

Carl Fausett

As promised - this is the "short list" of what has already been done:

> block was bored and steel sleeved, fitted with 2024 alloy low-expanison forged pistons to 1/2 of the piston-to-wall clearance that Mahle uses.

> pistons have graphite-impreganted skirts

> Engine static and dynamically balanced to within 0.1 gram

> Euro Heads Ported and Polished with 3-angle valve job

> Euro cams from the 310 HP series motor

> Aluminum Adjustable fuel distributor modified to flow 30% more fuel

> Euro WUR modified to react to boost, with set-screw adjustment.

> Two fuel pumps in series producing up to 450 LPH of fuel at 180 PSI max.

> Every inch of fuel system from back-to-front inspected for restrictions. Example: found 3 places where the Porsche rubber/reinforced fuel hose on the outside was 10mm in size, but on the inside hiding brazed barbed fittings that were 3.8 or 4 mm in ID. (Reference: a stock Honda 4 cyl car has 4mm fuel lines) Complete fuel supply system opened to 7.5 mm minimum.

> WUR mounted off the motor to keep it cooler and in "coldstart" richness...

> all fuel ines to injectors changed to -4AN (300% of stock)

> Headers, and 3.5" exhaust system. No cats. No muffler. One resonator.

> 928 Motorsports Fuel Enrichment System provided fueling to 6200 RPM at 6 psi on 1200 CFM air flow

> air-to-water intercooler system moving up to 3 GPM though the intercooler,
at 80% efficiency.

I know there's more - but that's all I can think of at the moment. Anyway - if you hear of a CIS motor making more HP on pump gas than this, let me know. I need to talk to that guy.

PS: I have a line on some CIS injectors that may be larger.....! (Hoping)